The present invention relates to a method of inspecting various running control functions of a motorcar, such as a traction control system and a limited slip differential mechanism and the like, which function to control the rotation of wheels according to the difference in rotational speed between the front and rear wheels or between the right and left wheels of the motorcar, and also relates to an apparatus to be used in carrying out the method.
The traction control system functions to operate in the following manner. Namely, a ratio of slippage is calculated based on the difference in rotational speed between driven wheels which correspond to one of the front and rear wheels and driving wheels which correspond to the other of the front and rear wheels. The rotation of the driving wheels is then controlled to keep the ratio of slippage within a predetermined range. As this kind of method of inspecting the traction control system, there is conventionally known a method in Japanese Published Unexamined Utility Model Registration Application No. 84544/1988. In this method, each of the wheels of a motorcar is mounted on each of rolls of an inspecting apparatus and an accelerator pedal is depressed in such a condition that each of the rolls is made to be freely rotatable. A judgement is thereby made whether the traction control system is acceptable or not based on the increase in the rotational speed of the rolls for the driving wheels within a predetermined time.
In the above-described Application No. 84544/1988, there is also described a method in which the accelerator pedal is depressed in a condition in which one roll for one of the right and left driving wheels is braked and in which a judgement is then made whether the limited slip differential mechanism is acceptable or not based on the value of increase in the rotational speed of the other roll for the other of the driving wheels within a predetermined time.
The above-described method of inspecting the traction control system has been made taking note of the following fact. Namely, at the time when the accelerator pedal is depressed, there occurs a difference in rotational speed between the driving wheels and the driven wheels (which will not rotate). If the traction control system operates normally, the increase in the rotational speed of the driving wheels is restrained and, consequently, the value of increase in the rotational speed of the rolls for the driving wheels within a predetermined time falls below a predetermined value. The same applies to the inspection of the limited slip differential mechanism.
However, even in case the traction control system and the limited slip differential mechanism do not function normally, there is sometimes a case where the value of increase in the rotational speed of the rolls within the predetermined time falls below the predetermined value, depending on the degree of depressing the accelerator pedal. It follows that the result of the inspection in such a case is judged to be acceptable in the above-described method of inspection. This brings about an inaccurate judgement.